They don't come any larger than 0.3 karats, which is too small for a solitaire. You can't get them to match either, which makes them bad for side stones. I tried.

A good alternative is Canadian diamonds, which are not owned by DeBeers, not mined or polished by slaves, and not the cause of any conflict. That solves about half the problems with diamonds.

Get them from Brilliant Earth (I'm not employed there, just a very satisfied customer.)